Dual reciprocating bellows pump with interlock shaft means

ABSTRACT

It is sought to provide a dual reciprocating bellows pump having two, i.e., left and right, bellows interlocked by interlock shafts to each other, which is free of wear powder or wear dust generated by the frictional movement of the interlock shafts and bearings relative to one another from pump feed fluid in pumping chambers, permits ready use of synthetic resin as pump element material, is excellent in function and cost and readily permits size reduction design.  
     Paired interlock shafts coupled to end members  6  of the pair of, i.e., left and right, bellows, are disposed in paired working air chambers  8,  and are movably inserted in through bores provided in a pump head. Between each interlock shaft and each through elastic seal members are disposed, thus sealing the left and right working air chambers  8  from each other. No particular bearing is used for the interlock shafts. Lip seals are desirably used as the elastic seal members.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to dual reciprocating bellows pumps withinterlock shaft means, in which a pair of expansible and contractablecylindrical bellows, with a pump head interposed therebetween, areinterlocked by paired interlock shafts as the interlock shaft means toeach other, with the inside of the cylindrical bellows made to bepumping chambers for pump fed fluid such as semiconductor processingliquid and with the outside of the cylindrical bellows provided withworking air chambers defined by a pump housing.

2. Description of the Prior Art

In this type of dual reciprocating bellows pump, interlock shaft meansis provided to couple together a pair of, i.e., left and right, bellows,so as to interlock these bellows to each other. An arrangement of thistype with the interlock shaft means disposed outside a pump housing andalso another one with interlock shaft means disposed inside pumpingchambers are well known in Japanese Patent disclosure No. 2003-314458.In the former arrangement, the interlock shaft means is coupled to theextended ends of a member, which is movable in unison with the bellowsand is extended to the outside of the pump housing. In the latterarrangement, a pump head disposed at the center of a pump housing hasthrough bores open in pumping chambers, and interlock shafts areinserted through the through bores to be in frictional contact with thebore inner periphery. The interlock shafts have their ends extendinginto the pumping chambers and operatively coupled to end membersprovided on the free ends of the bellows.

In the above prior art dual reciprocating bellows pump arrangement, inwhich the interlock shafts are disposed outside the pump housing, thecoupling mechanism for transferring the bellows operation to theinterlock shafts is complicated, and also the pump size and cost ofmanufacture are increased. In the case of the arrangement with theinterlock shafts disposed inside the pumping chambers, the interlockshafts are in close frictional contact with the through bores of thepump head for isolating fluid in the pumping chambers. Therefore, wearpowder or wear dust is generated in the frictional parts and introducedas undesired impurity in the pump feed fluid in the pumping chambers.Particularly, this poses very serious problems in the case, in which thepump feed liquid is semiconductor processing liquid with high purityrequired thereto.

In the pump, in which semiconductor processing liquids or chemicals aredealt with as shown in the above, richly corrosion-resistant syntheticresin is used in lieu of metal as the material the contact-with-liquidmaterials in the pumping chambers, and up to date pumps, in which allthe pump constituents are all made of synthetic resin, are spreadbecause they are desired in view of function and cost. As shown, even inthe case of adopting a pump arrangement using synthetic resin for thecontact-with-liquid parts, so long as the interlock shafts are disposedin the pump chambers, no grease or like lubricant can be used for thefrictional parts between the pump head and the through bores. Also, thecarbon-containing resin excellent in the frictional property can not beused due to the occurrence of corrosion resistance and wear particles.Accordingly, it is inevitable to adopt an arrangement, in whichsynthetic resin interlock shafts are in close frictional contact withthrough bores of a synthetic resin pump head via synthetic resinbearings. Thus, even slight distortion at the time of assembling appliesgreat load on the frictional parts to give rise to a “scratch”phenomenon and disturb smooth movement of the interlock shafts and, inan extreme case, results in the stop of the pumping operation.

This invention is made in view of the above various problems, and itsobject is to provide a dual reciprocating bellows pump with interlockshaft means, which can prevent intrusion of undesired impurities in thepump feed liquid, is excellent in function and cost and permits readysize reduction design.

SUMMARY OF THE INVENTION

To attain the above object of the invention, according to the inventionit is sought to provide a dual reciprocating bellows pump with interlockshaft means comprising a pump housing, a pump head assembled in the pumphousing at the center along the longitudinal axis thereof and capable ofwithdrawing and discharging pump feed liquid, a pair of, i.e., left andright, bellows having respective end parts sealedly mounted on the pumphead and capable of expansively and contractably, reciprocating with apredetermined stroke in the pump housing in longitudinal directionsthereof, paired end members each sealedly coupled to the free end ofeach bellows and capable of cooperating with the pump head definingpumping chambers inside the bellows and also defining working airchambers between the bellows and the housing, paired interlock shaftseach having the two ends coupled to the pair of end members such as tocause reciprocation of each bellows in an interlocked relation to thereciprocation of the other bellows, inserted through through boresformed in the pump head and capable of being displaced in thelongitudinal directions of the pump housing, working air feed means forselectively feeding working air to the part of, i.e., left and right,working air chamber, and paired valve means mounted on the pump head incorrespondence to the pumping chambers, respectively, in the pair of,i.e., left and right, bellows reciprocated in response to pressurechanges of working air fed by the working air feed means, forcontrolling the flow of the pump feed fluid into and out of the pumpingchamber, wherein : said through bores formed in the pump head are openin the pair of, i.e., left and right, working air chambers; saidinterlock shafts extend through said through bores into the pair of,i.e., left and right, working air chambers; and seal means is providedbetween said interlock shaft and the corresponding through bore of thepump head so as to isolate said pair of, i.e., left and right, workingair chambers.

In the above arrangement according to the invention, the interlockshafts extend, in their state open to the left and right working airchambers, through through bores provided in the pump head into theworking air chambers, and are not disposed in the pumping chambers. Sealmeans are provided between each through bores and each working airchamber, whereby the left and right working air chambers are isolated.Here, no bearing means for supporting any interlock shaft is needed.

According to the invention, it is also sought to provide a dualreciprocating bellows pump with interlock shaft means, wherein the sealmeans each include a cylindrical guide member open at the two ends,inserted and secured in each through bore of the pump head extendinginto the left and right working air chambers, and paired elastic sealmembers each mounted in each open end of the guide member, the interlockshafts are each movably inserted in each cylindrical guide member, theinner diameter of the cylindrical guide members being greater than theouter diameter of the interlock shafts, and the elastic seal memberseffect isolation of the left and right working air chambers in sealedcontact with the interlock shafts.

In the above specific arrangement of said seal means according to theinvention, said cylindrical guide members are inserted through andsecured in the through bores, and said elastic seal members are mountedon the two open ends of the guide members to be in sealed contact withthe interlock shaft movable in said guide members. In the contact parts,a seal action of isolating the left and right working air chambers isexecuted. The inner diameter of the cylindrical guide members is set tobe greater than the outer diameter of the interlock shafts, and thusthere is no possibility that the movement of the interlock shafts isinterfered in contact with the cylindrical guide members.

According to the invention it is further sought to provide a dualreciprocating bellows pump with interlock shaft means, wherein the innerdiameter of the through bores of the pump head is greater than the outerdiameter of the interlock shafts, and paired elastic seal members aredisposed in the through bores such as to be able to be in sealed contactwith the interlock shafts, thereby effecting the isolation of the leftand right working air chambers.

In the above specific arrangement according to the invention, theinterlock shafts are directly inserted through the through bores of thepump head, and a pair of elastic seal members are disposed in eachthrough bore between the interlock shaft and the through bore. Again inthis case, no bearing for supporting any interlock shaft is provided.

According to the invention, it is further sought to provide a dualreciprocating bellows pump with interlock shaft means, wherein saidelastic seal members are constituted by lip seals.

In the above specific arrangement according to the invention, theelastic seal members are each constituted by a so-called lip seal havinga thin tong-like seal contact part. The lip seals are richly flexible,and can thus absorb even a slight distortion at the time of the pumpassembling. During the pump operation, the left and right bellows areheld in a pressurized state by working air. With this pressure balance,the bellows are thought to be horizontally reciprocating without greatdistortion. Thus, no greater load than on the interlock shaft in sealedcontact with the lip seals is applied to the lip seals.

According to the invention, it is further sought to provide a dualreciprocating bellows pump with interlock shaft means, wherein the pumpconstituent elements are all made of synthetic resin.

In the above specific arrangement according to the invention, syntheticresin is used as the material of the pump constituent members inclusiveof contact-with-liquid members of the pumping chambers accommodatingpump feed fluid, that is, all resin pump design is made.

According to the invention, since the interlock shafts are disposed inthe working air chambers outside the bellows, there is no possibilitythat wear powder and wear dust are introduced into fluid in the pumpingchambers defined in the bellows. Also, since the interlock shafts aredisposed inside the pump housing, the coupling structure with respect tothe bellows is simple, and size reduction design of the entire pump canbe readily made.

Furthermore, the left and right bellows are held in a state pressurizedby working air with the pumping operation. With this pressure balance,seal means for isolating the working air chambers between interlockshafts and through bores of the pump head penetrated by the interlockshafts, undergo reciprocation substantially horizontally withoutgeneration of great distortion, and thus it may be of a relativelysimple arrangement. Besides, since no particular bearing is necessarybetween each interlock shaft and each through bore, the load on theinterlock shafts is reduced, and it is possible to obtain smooth pumpingoperation.

Thus, in the case of adopting the arrangement that cylindrical guidemembers for guiding the interlock shafts in the movement thereforeinserted through and secured to the through bores, the interlock shaftswill not be in direct frictional contact with the guide members in theirmovement by setting the inner diameter of the guide members to begreater than the outer diameter of the interlock shafts. As the seal,the elastic seal members mounted on the open ends of the guide memberscan sufficiently effect isolation of the working air chambers.

In the case of the arrangement without provision of any cylindricalguide member, by setting the inner diameter of the through bores to begreater than the outer diameter of the interlock shafts, a pair ofelastic seal members is disposed between each through bore and eachinterlock shaft. Thus, it is not only possible to avoid the frictionalcontact of the interlock shafts with the corresponding through boresduring movement, but also effect sufficient isolation of the working airchambers with the pair of elastic seal members.

Moreover, by using lip seals as the elastic seal members, it is possibleto obtain soft contact with the interlock shafts and absorb even slightdistortion at the time of the pump assembling in the contact parts. Theload on the interlock shafts thus can be further reduced.

With the arrangement as shown above, according to the invention, byusing synthetic resin as the material of various pump constituentmembers such as contact-with-liquid parts of the pumping chambersaccommodating pump feed fluid, all resin pump design can be readilymade, and it is possible to provide a pump, which is suited for dealingwith semiconductor processing liquids or chemicals as the pump feedfluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more apparent upon a reading of the followingdetailed specification with reference to the accompanying drawings, inwhich:

FIG. 1 is a schematic sectional view showing a first embodiment of thedual reciprocating bellows pump with interlock shaft means according tothe invention;

FIG. 2 is a fragmentary enlarged-scale view showing the pump shown inFIG. 1;

FIG. 3 is a fragmentary sectional schematic view showing a secondembodiment of the dual reciprocating bellows pump with interlock shaftmeans according to the invention;

FIG. 4 is a fragmentary enlarged-scale view showing the pump shown inFIG. 3; and

FIG. 5 is a fragmentary view showing a modification of the lip sealshown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described withreference to the drawings. FIGS. 1 and 2 show the first embodiment ofthe dual reciprocating bellows pump with interlock shafts as interlockshaft means. Reference numeral 1 designates a pump housing. Referencenumeral 2 designates a pump head disposed in the pump housing 1 at thecenter thereof in the longitudinal axis X-X. The pump housing 1comprises a pair of, i.e., left and right, parts with the pump head 2 asa border. These parts are assembled to be integral with the pump head 2by a pair of assembling frames in a stage positioned by pins 3.

Reference numeral 5 designates a pair of, i.e., left and right,cylindrical bellows, which have their stem parts 5 a mounted in a sealedstage on the central pump head 2 and expansively and contractablyreciprocal with a predetermined stroke along the longitudinal axis X-Xof the pump housing 1. Reference numeral 6 designates end members, whichare each coupled in a sealed state to the free end of each bellows 5,each define a pumping chamber 7 in each bellows 5 in cooperation withthe pump head 2 and define a working air chamber 8 between each bellows5 and the pump housing 1. In this embodiment, the end members 6 areformed to be integral with the bellows 5, respectively.

Reference numeral 10 designates interlock shafts constituted as theinterlock shaft means, which are inserted through through bores 11 opento a pair of, i.e., working air chambers 8, and extend into the workingair chambers 8, respectively. Each free bellows end part is coupled bybolts 14 to each end member 6 via two coupling members 12 and 13. Thetwo coupling members 12 and 13 are mounted by the bolts 14 to thecorresponding end member 6 such as to sandwich the end member 6. Thepair interlock shafts 10 are provided face to face in the working airchambers 8 in concentric positions in radial direction centered on thelongitudinal axis X-X. These interlock shafts 10 are movable along andparallel with the axis X-X such that one of the bellows 5 is interlockedwith good balance to the reciprocation of the other bellows 5 along theaxis X-X.

Reference numeral 15 designates paired cylindrical guide members, whichare each inserted in and secured to each through bore 11. Each interlockshaft 10 is movably inserted in each guide member 15. As shown in FIG.2, the inner diameter ID of the guide members 15 is set to be greaterthan the outer diameter OD of the interlock shafts 10. When eachinterlock shaft 10 is moved in the longitudinal direction, it is not infrictional contact with the inner periphery of the guide member 15 owingto a gap G held between it and an elastic seal member 16 to be describedlater.

The elastic seal members 16 have a ring-like shape, and are mounted onthe open end parts 15 a of each cylindrical guide member 15 to be inelastic contact with the outer periphery of the interlock shaft 10, thuseffecting the sealed contact. As the elastic seal members 16, it isparticularly desired to use thin tong-like lip seals as in thisembodiment.

Each elastic seal member 16 constituted by a lip seal is secured in itsstate that it is pushed against the open end part 15 a of the associatedcylindrical guide member 15 and with its stem part 16 a clamped from theback side by a back-up member 17, and its tong part 16 b extendingradially inwardly is elastically held in sealed contact with the entireouter periphery of the associated interlock shaft 10. Thus, the pair of,i.e., left and right, elastic seal members 16 isolate the flow ofworking air in the left and right working air chambers 8.

Working air feed switching mechanisms 18 mounted on the opposite endparts of the pump housing 1 selectively feed working air from an airsource 19 via a control valve 20 to the part of, i.e., working airchambers 8. When working air is thus fed to one of the working airchambers 8, the associated bellows 5 undergoes contracting movement,which is transmitted via the interlock shafts 10 to the other bellows 5,while causing release of the working air from the other bellows 5 tocause expansion movement thereof. This operation is repeated.

The working air feed switching mechanisms 18 each include an air inletport 21, an air discharge port 22, a piston 23 and a cylinder 24, andthey constitute an operating air feed means together with the controlvalve 20 and the air source 19 connected via ducts 25 to 28 to them.This means may be the same as what is disclosed in Japanese PatentDisclosure No. 2003-314458, and its detailed arrangement is notdescribed.

The left and right bellows 5 repeatedly undergo expansion andcontracting movement in response to the working air feed switchingoperation to cause pumping operation of withdrawing and discharging pumpfeed fluid such as semiconductor processing liquid or a chemical liquidaccommodated in the pumping chambers 7 in the bellows 5. The in-flow andout-flow of the pump feed liquid to and from the pumping chambers 7 areeffected via valves 30 provided on the pump head 2. Each pumping chamber7 has a withdrawal guide and a discharge guide valve 30 provided as apair. In FIG. 1, these paired valves 30 are shown side by side in thedirection of the paper surface, and only one set of the paired valves 30is seen. These valves are communicated with withdrawal and dischargeports (not shown) provided on the pump head 2. The arrangement in thispart is the same as what is disclosed in the above Japanese PatentDisclosure No. 2003-314458, and its detailed description is not given.

In the dual reciprocating bellows pump having the above arrangement, asdescribed above the pumping operation is executed in such a manner thatthe pair of, i.e., left and right, bellows 5 undergoes reciprocationalong the longitudinal axis X-X in a state that they are interlocked toeach other by the interlock shafts 10 in response to the selective feedof working air. In this operation, the left and right working airchambers 8 are always in a state pressurized by working air and heldbalanced. The bellows 5 thus are not excessively deviated from thedirection of the axis X-X and distorted or do not bring aboutvibrations. Thus, the interlock shafts 10 are likewise movedsubstantially along the direction of the axis X-X, and they do not tocome to be in excessive contact with the cylindrical guide members 10and can be moved smoothly. With this arrangement, the interlock shafts10 do not require any special bearing, but require only the elastic sealmembers 16, which isolate the left and right working air chambers 8 andare solely in contact at the time of the usual movement. The load on theinterlock shafts 10 is thus extremely reduced, and the generation ofwear powder, wear particles and wear dust from the contact parts aresuppressed as much as possible.

The pump constituents may all be readily manufactured from syntheticresin. Particularly, it is desirable to use richly corrosion-resistantsynthetic resin for the contact-with-liquid parts of the pumping members7 accommodating the pump feed liquid, such as the bellows 5, the pumphead 2 and the valve 30. The interlock shafts 10 and cylindrical guidemembers 15 are desirably made of such synthetic resin as PEEK(polyeterethylketone) resin. The lip seals constituting the elastic sealmembers 16 are desirably filler-containing PTFE(polytetrafluoroethylene) resin.

When the lip seals made of the filler-containing PTFE resin is incontact with the interlock shafts 10 made of PEEK, PTFE is transferredas initial wear to the frictional surfaces of the shaft 10. As a result,the lip seals of the filer-containing PTFE come to be in frictionalcontact with the filler-containing PTFE having been transferred to thesurfaces of the PEEK resin. Thus, the wear does not proceed greatly. Itis thus an advantage that the sole lip seals permit sufficient seal, sothat no particular bearing is necessary.

FIGS. 3 and 4 show a second embodiment of the dual reciprocating bellowspump according to the invention. In the figures, elements like those inthe preceding first embodiment are designated by like referencenumerals, and their description is not given in detail. In thisembodiment, the inner diameter of the through bores 11 formed on thecentral pump head 2 is set to be greater than the outer diameter of theinterlock shafts 10. In each through bore 11, a pair of, i.e., left andright, ring-like elastic seal members 16 are disposed in a spaced-apartrelation to each other and held in contact with the interlock shaft 10inserted through the through bore 11, thus blocking the flow of workingair in the left and right operating air chambers 8 to effect isolationof the two chambers 8.

The second embodiment of the pump is simpler in arrangement than thefirst embodiment with omission of the cylindrical guide members 15.Here, the elastic seal members 16, like the first embodiment, areconstituted by thin tong-like lip seals. As shown in an enlarged scalein FIG. 4, each elastic seal member 16 constituted by a lip seal has anL-shaped sectional profile, and its stem part 16 a is secured in athreaded annular recess 31 formed on each side of the pump head 2 byscrewing a threaded ring-like seal retainer 32 in the recess 31.Reference numeral 33 designates a tool insertion bore formed in the sealretainer 32. The seal retainer 32 is fitted in the annular recess 31 byinserting a suitable tool. A tong part 16 b of the lip seal 16,extending from the stem part 16 a and bent radially inwardly, is inelastic frictional contact in a ring-like form on the entire outerperiphery of the interlock shaft 10, thus effecting a seal contacttherein. Thus, during their moving operation the interlock shafts 10 arein contact only with these elastic seal members 16 and not in directcontact with the inner surfaces of the through bores 11 of the pump head2. Thus, again in this embodiment no particular bearing for theinterlock shafts 10 is necessary.

FIGS. 3 and 4 are provided for describing one interlock shaft 10 andrelative arrangement thereto. However, like the first embodiment a pairof interlock shafts 10 are disposed in the working air chambers 8. Also,as the material of these constituent members, like the first embodimentall the elements can be readily made from appropriate resin.

FIG. 5 shows a modification of the lip seal constituting the elasticseal member in corresponding to the part shown in FIG. 4. As in the sealretainer 32 in the second embodiment, the stem part 16 a is formed tohave an enlarged shape so that it also serves as the seal retainer 16shown in the second embodiment. Here, the stem part 16 a of the lip seal16 is held in an annular recess 31 without thread such that it is pushedfrom the outside by the end face 1 a of the housing 1, and the thin tongpart 16 b extends such that it is bent radially inwardly to be in sealedcontact with the outer periphery of the interlock shaft 10.

As shown, the elastic seal member 16 may be of various shapes, but itspart in contact with the interlock shaft 10 is desirably of a thintong-like shape.

While preferred embodiments and modifications of the arrangementaccording to the invention have even described with reference to thedrawings, the interlock shafts 10 are shown to be of rod-like shape.However, it is possible to use any other shape such as angular shapes aswell, and the illustrated arrangement is by no means limitative.

1. A dual reciprocating bellows pump with interlock shaft meanscomprising; a pump housing; a pump head assembled in the pump housing atthe center along a longitudinal axis thereof and capable of withdrawingand discharging pump feed liquid; a pair of left and right cylindricalbellows having respective end parts sealedly mounted on the pump headand capable of expansively and contractably reciprocating with apredetermined stroke in the pump housing in longitudinal directionsthereof; paired end members each sealedly coupled to the free end ofeach bellows and capable of cooperating with the pump head definingpumping chambers inside the bellows and also defining working airchambers between the bellows and the housing; paired interlock shafts assaid interlock shaft means, each having the two ends coupled to the pairof end members such as to cause reciprocation of each bellows in aninterlocked relation to the reciprocation of the other bellows, insertedthrough through bores formed in the pump head and capable of beingdisplaced in the longitudinal directions of the pump housing; workingair feed means for selectively feeding working air to the pair of leftand right working air chambers, and paired valve means mounted on thepump head in correspondence to the pumping chambers, respectively, inthe pair of left and right bellows reciprocated in response to pressurechanges of working air fed by the working air feed means, forcontrolling the flow of the pump feed fluid into and out of the pumpingchambers; wherein: said through bores formed in the pump head are openin the pair of left and right working air chambers; said interlockshafts extend through said through bores into the pair of left and rightworking air chambers; and seal means is provided between said interlockshaft and the corresponding through bore so as to isolate said left andright working air chambers.
 2. The dual reciprocating bellows pump withinterlock shaft means according to claim 1, wherein: said seal meansincludes a cylindrical guide member open at the two ends, inserted andsecured in said through bore of the pump head and extending into theleft and right working air chamber, and an elastic seal member mountedin said open ends of the guide member; said interlock shaft is movablyinserted in said corresponding cylindrical guide member, the innerdiameter of the cylindrical guide member being greater than the outerdiameter of said interlock shaft; and said elastic seal member effectsisolation of the left and right working air chambers in sealed contactwith said corresponding interlock shaft.
 3. The dual reciprocatingbellows pump with interlock shaft means according to claim 1, wherein:said inner diameter of said through bore of the pump head is greaterthan the outer diameter of said interlock shaft; and an elastic sealmember is disposed in said corresponding through bores such as to beable to be in sealed contact with said interlock shaft, therebyeffecting the isolation of the left and right working air chambers. 4.The two-ganged interlock bellows pump with interlock shaft meansaccording to claim 3, wherein; said elastic seal member is constitutedby a lip seal.
 5. The dual reciprocating bellows pump with interlockshaft means according to claim 4, wherein: said pump constituentelements are all made of synthetic resin.